A computer network is any set of computers coupled to each other with the ability to exchange data. The interconnections between computers enable communication with a variety of different kinds of media, including twisted-pair wires, coaxial cables, fiber optic cables, power lines, Ethernet and various wireless technologies. Faster interconnections generally improve network performance by reducing latency and increasing communication bandwidth. Higher bandwidths enable desirable services such as social media, video conferencing, multi-media transfers, etc. Further, an increased capacity for uploads and downloads can create a huge boost in productivity for any individual or business entity—the speedier the connections, the better the network's utility to its users.
The interconnections (such as fiber optic cables, twisted pair wires, coaxial cables, etc.) carry analog electrical or optical signals between transceivers. The signal may be, for example, an electrical voltage, an electrical current, an optical power level, a wavelength, a frequency, or a phase value. The receiver receives the signal, converts that analog electrical or optical signal into digital format, and extracts the transmitted data stream for use by the receiving node. The analog-to-digital conversion often employs a flash analog to digital converter.
A flash analog to digital converter is a type of fast converter that uses a linear voltage ladder and a comparator at each “step” in the ladder. The comparators operate in parallel to compare the input voltage to each of the reference voltages. Often these ladders are constructed of a series of resistors, but capacitive voltage division is also possible. Though flash converters are extremely fast, they typically require a large number of comparators relative to other analog to digital converter implementations, especially as the precision increases. A flash converter requires 2n-1 comparators for an n-bit conversion. The output of these comparators is generally fed into a digital encoder which converts the inputs into a binary value.
The Institute of Electrical and Electronics Engineers (IEEE) has published IEEE Std 802.3ba-2010, a standard which provides for Ethernet communications at rates as high as 100 Gb/s. The standard specifies the signaling rate for individual channels can be as high as 25 Gb/s. Since the fundamental limit for transistor switching in the 65 nm silicon integrated circuit manufacturing process is below 40 Ghz, the new IEEE standard places high demands indeed on the implementation of the analog to digital converter.